In wireless communications, a part of the process of delivering a call to a mobile phone may involve the serving, i.e., last registered, mobile switching center (MSC) broadcasting a page message to all of the cells located within the last registered MSC's serving area. A cell is a basic geographic unit of a cellular system. Cells may be grouped geographically into two or more Location Areas (LAs). A cell includes a transmission tower that is generally centrally disposed within the cell, although multiple transmission tower locations may be supported to ensure adequate coverage, particularly in problem areas.
Page messages are radio frequency signals transmitted by some or all of the transmission towers associated with a MSC. Page messages are used by MSCs to locate and alert a specific mobile phone that there is a call for it. A first page attempt is generally sent by all of the transmission towers in the mobile phone's last seen location area. If the specific mobile phone successfully receives and responds to the page message with the proper acknowledgement message, then the call delivery process can continue.
If the mobile phone does not respond to the first page attempt, a larger area, known as a Location Area Cluster (LAC), may be paged during second and third page attempts. The LAC usually consists of every location area or MSC that borders the last seen location area. The last registered MSC will send Inter System Page (ISPAGE) messages to the border MSCs. The ISPAGE messages instruct border MSCs to transmit page messages intended for the mobile phone.
FIG. 1 shows an illustrative view of a network of MSCs. Typically, the first page attempt involves the last registered MSC, i.e., MSC 1, paging all of the cells in the last seen location area (LA), i.e., MSC 1 pages LA 2. The first page attempt usually results in a high response rate, i.e., page reception and response by the specific mobile phone. Second and third page attempts involve a) the last registered MSC, i.e., MSC 1, paging all of MSC l's cells, i.e., MSC 1 pages LA 2 and LA 1, and b) border MSCs, i.e., MSC 2, MSC 3, MSC 4 and MSC 5, paging cells that border areas of the last seen location area (LA), i.e., MSC 2 pages LA 3, MSC 3 pages LA 5, MSC 4 pages LA 7, and MSC 5 pages LA 9 and LA 10. Second and third page attempts result in significantly lower response rates, e.g., approximately 5%.
The volume of calls that MSCs can deliver to mobile phones translates directly into revenue for a service provider. Disadvantageously, in large metropolitan markets, a MSC's paging resources may be the limiting factor that prevents the MSC from delivering a higher number of calls to mobile phones, thus reducing the revenue potential for the service provider. Also disadvantageously, the ISPAGE page mechanism produces a large percentage, i.e., approximately 50%, of the total page messages.